Russell T Davies was responsible for the most influential drama of the decade - the return of Doctor Who. Not only did it single-handedly save Saturday nights on BBC1, it also reinvented the concept of TV family drama, inspiring the likes of Robin Hood, BBC1's upcoming Merlin, and ITV1's Primeval.

Two doctors and four series into its second coming - with David Tennant in the lead role accompanied by assistant Catherine Tate - Doctor Who is as strong as ever, surviving first the exit of Christopher Eccleston and then his original sidekick, played by Billie Piper.

Russell T Davies. Photograph: Eamonn McCabe Eamonn McCabe/Guardian
But the next series in 2010 will have to do without Davies, who is stepping down from his "showrunner" role to be replaced by one of the show's most highly regarded scriptwriters, Coupling creator Steven Moffat.

So Davies - named by one newspaper as the most influential gay man in Britain and awarded an OBE this year - will no longer be in charge of BBC1's most important show, although he will write part of the five specials due to be broadcast next year.

Nevertheless, he retains a place in the MediaGuardian 100 because freed from the gruelling constraints of the Doctor Who filming schedule, he can now move onto other projects. And given his success with the time-travelling doctor, that means he can do just about anything he wants.

Davis is currently mulling over two drama ideas for grown-ups, one of which will be about gay men in their 40s, with the BBC having first refusal.

It is an area in which he has excelled in the past, including shows such as Channel 4's Queer as Folk, ITV1's The Second Coming and Bob & Rose, and BBC3's Casanova.

Davies began his career as a BBC researcher and went on to work for children's shows Why Don't You? and Children's Ward, for which he won a Bafta, before moving into prime time drama with Coronation Street and drama Touching Evil.

Not only does Doctor Who continue to dominate Saturday nights, it has spawned two spin-off series: Torchwood, first on BBC3 and now on BBC2; and the Sarah Jane Adventures on the CBBC channel.

It will be fascinating to see what Moffat does with Doctor Who when he takes over next year. But not half as interesting as what Davies does next.

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